1. Field of the Invention
The present invention relates to an aircraft passenger seat frame which is structured to be relatively lightweight, while having an increased strength-to-weight ratio which is capable of withstanding substantial forces, as set by various dynamic and static testing criteria of the Federal Aviation Association (FAA) for aircraft seating. Moreover, the seat frame is structured of sufficient strength to be highly adaptable to a variety of mounting postures dictated by an interior configuration of the aircraft and/or surrounding fixtures, without requiring extensive structural modification thereof to maintain minimum strength requirements, but while maintaining the seat frame's overall, lightweight nature.
2. Description of the Related Art
The field of art relating to aircraft passenger seating, and especially custom aircraft seating is very specialized, especially in light of the balance that must be attained between luxury and comfort and the various strict guidelines and requirements which must be met by any design prior to installation into an aircraft. In particular, the FAA is charged with setting forth the various guidelines and requirements which must be met by aircraft components, and in doing so has established a series of dynamic and static tests which test the minimum load or impact requirements of an aircraft component, and an aircraft seat in particular. For example, relevant FAA regulations which the manufacturers of aircraft seats are required to meet are found in FAR 25,562; NAS 809; and AS 8049.
As with many federal safety regulations, it is not until after ratification of new guidelines that the increased safety requirements take effect in the market place. Such is the case with the most recent FAA requirements calling for even greater safety of aircraft components that must first successfully complete testing under substantially greater forces and impacts. The new FAA regulations have now begun to affect manufacturers of aircraft components and consequently, the availability of such products for consumers to choose from.
Specifically, there are presently a number of dynamic tests which an aircraft seat must undergo in order to test various parts of the structural integrity of the seat frame and to determine its safety and viability. Moreover, conscientious manufacturers often put their designs through rigorous added testing. One such test involves essentially a simulation of a head-on impact, wherein a substantial amount of force and/or strain is placed on the aircraft seat frame, first on the foundation and base of the aircraft seat, and subsequently, on the seat back portion of the frame as would be the case in a crash situation. The aircraft seat frame must be able to withstand vertical impact forces on its foundation and base, as well as horizontal or buckling forces on the seat back frame itself. The FAA's new requirements have substantially increased the amount of such forces which the aircraft seat frame must withstand during testing.
Presently, most conventional aircraft seat frame designs include generally thick walled metal tubing having rounded or squared configurations. In order to save weight, however, this tubing is generally hollow making it much more susceptible to bending or buckling. In particular, during the various impact tests, the seat foundation and seat base are subject to focused vertical forces which tend to bend the tubing. In order to overcome the increased susceptibility of the tubing to bending, especially under the more stringent FAA testing and safety requirements, prior art seat frame designs seek to increase the wall thickness and/or material thickness of the tubing, and/or seek to add additional tubing reinforcement members. While many of these prior art "solutions" provide sufficient strength to meet safety and testing requirements, there are several drawbacks associated therewith. In particular, and as previously mentioned, the increased cost associated with the use of more material and components is a significant disadvantage to such prior art seat frame designs, but the most significant consideration associated with aircraft design in general has to do with the weight of the components. In particular, most aircraft regulations have some significant size-to-weight requirements for the aircraft, meaning that less seating or cut-backs in other amenities must be implemented to meet the requirements. More importantly, however, for every added pound an aircraft must carry, the fuel consumption of that aircraft increases exponentially. Given the already expensive cost of aircraft fuel, and the many miles and hours logged by the aircraft, a substantial increase of fuel consumption, not to mention a substantial increases in wear which leads to earlier replacement requirements, significantly increase the up-keep costs of the aircraft. Accordingly, the strength-to-weight ratio can be said to be one of the most important criteria associated with aircraft design and aircraft interior design.
Additionally, aircraft seats are required to undergo what is known as a yaw test wherein the seat is propelled forward to an impact at a certain angle. As a result, when this test is performed, and further due to the use of a shoulder harness on some customized seat designs, a majority of the force of impact on the seat back will be focused at a single upper corner of the seat back and not the overall seat back. Presently, most conventional aircraft seat backs include the rounded or squared steel tubing to comprise the structure of the seat back. Such conventional seat backs, however, upon undergoing the yaw test will translate the majority of the impact through a single side rail of the seat back portion into the seat foundation. While most seat foundations will include a recline cylinder at one side of the seat frame which helps to provide some increased resistance to that force, most existing seat designs leave the side opposite the recline cylinder un-reinforced. Accordingly, if the force of impact in the 10 degree yaw test is directed at an opposing corner from the side at which the recline cylinder is mounted, the un-reinforced side of the seat foundation frame will bear all or most of the impact and is likely to fail. Consequently, seat frames known in the art are now being forced to provide substantially increased strength and/or thicker tubing in the seat foundation and seat back, or are unnecessarily utilizing a second recline cylinder disposed at the previously un-reinforced side of the seat foundation. These designs, however, while providing sufficiently increased impact resistance, also substantially increase the cost of the seat frame in materials and added parts, and more importantly will substantially increase the weight of the aircraft seat frame.
Still another FAA test preformed on aircraft seat frames, which has also recently been increased in severity, involves the buckling or flexing of the underlying support surface. Specifically, in certain crash situations, the underlying support surface or floor of the aircraft to which the seats are secured may tend to buckle, flex or otherwise bend. While this floor is preferably structured to maintain some sort of structural integrity during a crash situation, most conventional floor surfaces will waiver or buckle a substantial amount, partly to dissipate the impact forces and maintain its general, overall integrity. Still, however, the aircraft seat must be rigidly secured to the underlying support surface, thereby making it very susceptible to becoming completely or partially dislodged from the underlying support surface during such testing. As result, and in an attempt to solve the problems associated with such testing, others in the art have turned to larger, bulkier and accordingly, heavier securing structures to mount the seat to the underlying support surface. Such increases, however, can significantly add to the cost and overall weight of the seat, and can sometimes function to lessen the ability of the underlying support surface to maintain its structural integrity during the testing.
Yet another drawback to existing seat frame designs relates to the adaptability of the seat frame for securement at different mount locations and in different mount postures, while still meeting the rigorous FAA testing criteria. In particular, the precise mounting point of an aircraft seat is often dictated by the positioning of pre-set mount tracks of the aircraft. Indeed, the position of these mount tracks is often directly related to the structure of the aircraft and the load centers thereof, such that the mount tracks cannot be varied or repositioned in order to accommodate for the positioning of internal fixtures, such as seats. Rather, the internal fixtures must be made to correspond the acceptable mount positions provided by the mount tracks. Specifically, conventional mount track positions can vary from aircraft to aircraft along a longitudinal (front/back) direction as set by the spacing of the individual mount points of the track, or along a lateral (side to side) direction depending upon the spacing of each individual track from one another. Moreover, if other fixtures, such as seats, tables, etc. are also present and mounted, longitudinal, lateral, and height constraints for the seat positioning must be taken into account. This is especially the case with regard to custom seats that swivel or slide side to side and/or forward and aft. Such adjustable seats must be mounted with sufficient clearance from other fixtures and walls to allow a full range of movement, while still being mounted to the underlying support surface within the limited constraints of the mount tracks of the aircraft. Accordingly, it is sometimes the case that the upper, moving portions of the seat, namely the seat foundation portion and seat back portion are not aligned directly over the seat base portion that is secured at the mount track. Unfortunately, however, most conventional seat frame designs are pre-formed, welded assemblies that are assembled by the manufacturer well prior to installation, and therefore cannot be adapted to fit unique, specific installation requirements unless substantial design modification is achieved. Indeed, substantial re-tooling and redesign of the manufacturing process and design of the frame components must be undertaken by the manufacturer to make an acceptably mounted fit, a process which can be quite expensive and time consuming, especially since the precise mount requirements may not be known until the actual installation time. Additionally, as can be appreciated, however, any reworking of the frame or design changes implemented which affect the orientation of the seat frame, location of its center of gravity, etc., can also drastically affect the strength and crash worthiness of the seat, such that a frame design which in a normal configuration passes all tests will now fail those same tests due to the re-configuration. For this reason, and due to the general lack of adaptability of known seat frame designs regardless of strength considerations, independent seat frame designs have generally been implemented for each particular type of mounting situation. Of course, however, given the large number of different mounting possibilities, manufacturers must either have a very large number of different, specific frame designs, a costly and time consuming approach, or must make the seat frames of a sufficient added strength to compensate for the differences in mount locations and configurations, thus sacrificing adaptability and weight minimization.
Accordingly, there is a substantial need in the art to provide an aircraft seat frame which is capable of meeting the new and increased safety and testing requirements set forth by the FAA, and which at the same time is not substantially more heavy in weight and which does not have a greatly increased cost associated with production nor with the materials needed. As will be appreciated by those skilled in the art, if either the weight of or the cost associated with the aircraft seat frame is increased, it will severely and negatively impact the ability of the aircraft owner to fully equip the aircraft with as many passenger seats as possible and/or with other needed or desired equipment. Furthermore, such a seat frame design should also be adaptable to a variety of mount postures without having to sacrifice the strength and light weight nature thereof, and should be quickly adaptable at a time of installation in a manner which can take into account the variety of mounting constraints of several different aircraft.